Process for making oils from acid sludges resulting from the sulfuric acid purification of coal tar distillates



Patented Sept. 14, 1948 PROCESS FOR MAKING OILs FROM ACID SLUDGES RESULTING FROM THE SUL- FURIC ACID PURIFICATION OF COAL TAR nIsTILLA Es Harry L. Allen and George J. Skriver, Philadelphia, Pa., asslgnors to Allied Chemical & Dye Corporation, New York, N. Y., a corporation of New York No Drawing. Application September 29, 1945,

Serial No. 619,426

Claims. (Cl. 196-148) This invention relates to manufactureof oils,

and is directed more particularly to processes for making oils from acid sludges resulting from the sulfuric acid purification of coal tar distillates.

In known operations for refining crude coal tar oils by sulfuric acid treatment, there are produced large quantities of acid sludges which are usually disposed of as waste or sometimes burned as fuel. On account of their high acid and sulfur contents, such sludges are not satisfactory fuels.

We have discovered that these acid sludges contain certain hydrocarbon oils which have been found to be useful in the arts e. g. particularly in rubber compounding and in manufacture of resins.

A principal object of the invention is to provide processes which make possible the recovery of the herein described hydrocarbon oils from acid sludges of the type mentioned. A further object is provision of procedure for recovery of these oils in such a way as to obtain high yields of the sought-for oil products.

In carrying out the invention, the acid sludgeswhich may be employed as starting materials are those derived from sulfuric acid purification of crude coal tar distillate oils such as .crude benzol, toluol, crude naphthalene, crude solvent naphtha and crude hi-fiash solvent. Although compositions of such sludges vary widely, composition of representative suitable acid sludges are about as follows: 20-60% H2804, 0.l-%oi1 and naphthalene, and 350% pitch.

According to the invention, the acid sludge utilized is treated with water under conditions to form a mass comprising tarry material herein designated as acid pitch, and aqueous relatively weak sulfuric acid. Preferably, the raw acid sludge is diluted with to 25 parts by weight of water, agitated, and held at temperature of 75 to 102 C. for a period of time ranging from A to an hour, the equipment employed being such as to facilitate maintenance of agitation and the temperature conditions stated. This operation results in separation of the tar from the sludge and the leaching out of most of the sulfuric acid into the water layer. On settling for an interval of 3 to 4 hours, the mass stratifies to an under layer of relatively weak sulfuric acid and an upper layer of solid and semi-liquid acid pitch containing substantial quantity of occluded sulfuric acid. The impure weak sulfuric acid solution, which may have an H2504 concentration of 35 to 45%, and the acid pitch are separated by any suitable means e. grby drawing 011' the under layer'of weak acid. In this operation, at

least most of the weak sulfuric acid is separated from the acid pitch, although after decantation, the acid pitch usually contains an appreciable amount of weak sulfuric acid solution. The described water treatment step effects easy separation and removal from the crude acid sludges of certain water and/or acid soluble materials such as sulfonates which, if not thus removed, would be carried thru the process and be only diil'lcultly separable at a subsequent process stage or alter the character of the final product.

The acid pitch is then treated with a suitable neutralizing agent under conditions to completely neutralize substantially all of the remaining sul-- furic acid associated with the acid pitch. Neutralizing agents such as caustic soda, lime, sodium carbonate, calcium carbonate, and magnesia may be used for this purpose. To facilitate operation and procure adequate neutralization of residual sulfuric acid, the neutralizing agent is used preferably in the form of a Water solution containing suificient neutralizing material to completely neutralize residual sulfuric acid present in the acid pitch, the amount of water as such being enough as to form an acid pitch-neutralizing agent mass which is relatively fluid and readily agitatable; Neutralization is preferably carried out in a vessel equipped with an agitator and provided with means to maintain temperatures in the vessel from room temperature to about C., usual neutralizing temperature being about the boiling temperature of the mass formed by addition of the neutralizing solution to the acid pitch. Time required for neutralization may vary from 15 minutes to 5 hours depending upon physical nature of the acid pitch, 1. e. whether fairly finely divided or relatively lumpy. Usually, the quantity of water employed amounts to from 1 to 2 parts by weight of the acid pitch, and the quantity of neutralizingagent depends of course upon the H2504 content of the acid pitch, and the alkalinity of the specific neutralizing agent used in the particular operation. End point of the neutralization operation may be determined by any suitable test applied to a representative sample of the mass in the neutralizer.

When the condition of neutralization is attained,'the neutralized acid pitch may be separated from the aqueous phase as by filtration or centrifuging. If desired the separated acid pitch may be washed one or more times with water. Preferably, substantially all the aqueous phase is separated from the pitch, although in some instances the acid pitch may contain 10- 25% by weight of occluded water.

a44aocs The neutralized acid sludge is charged into a.

still which may be either cold or preliminarily heatedto moderate temperature, say. of the order of 150-175 C. The still is externally heated, i. e.

constructed and operated insuch-a way that there is no direct contact between hot fire gases and the body or batch of acid pitch undergoing distillation. The equipment is designedfor distillation at atmospheric pressure andrisprovided with a vapor offtake connected with the inlet of a suitable condenser. Regardless of particular construction of the still and the mode of.

heating, the operation is such that at the time of charging the still, vapor temperature of'any vapors more or less immediately exiting the distillation zone are about 1Q0-125C-. Firing of the s i l is ontroll d sothat. thereaftcrztemperature in the distillationnone increases, preferably at a el velvsmo th: radient.- to a point such that vapor temperature of the oil vapors exiting il a n approa hes but. does. not substantially exceed 40o C. 'We findthatatsignificantly higher vapor temperatures, the oil products of the invention begin to decompose, Distillation of'the body of. aci pitch; is carried out in the d i n on in. he. a sence of xtraneous steam, x zin ma er a r. other modifyin agent which might alter: the characteristic properties of the product; oils. Thisgandtbe distillation of the acid pitch at: atmospheric pressure are important featuresof; thisinvention. We have found vacuumdistillation which a chemist w d n rmal y. use. to btain mex mum'y el o oil does-not for-m the desired;-products-since it results in (a ss. d sirable oils, containin s stantially less low boilingconstituentsand (b) a less valuable distillation residue. of (a, plastic character difficult tohandle as contrasted with the coke-like rcsidue'resultingfrom distillation carried out a mosph r pre sur The distillation operation. is proceeded with for a period of time such that the-distillation zone residue is reduced; to, arel-atlvely dry, solid, coke.- like mass. Distil ati nti ably eepenei-ngprincipai uponthes ze f the id p tch ar e; nd upon thevdesi n. o the particular equipment employed; q

The vapors dlschar ediromrxthei distillation zone may be .cndensed:in anvsuita le-way. .Th resulting oily condensate is, an;oijlihredomin tly aromatic in character and having aboiling range of 75 -400" C. and; specific gravit rat: 2.5.5" .C.-.of 0990-1000. The oils, obtained-fly the. foregoing process have physical and chemical charact eris-- tics differing substantiallyfromoi-lsobt ined by destructive distillation; of: sludges-or. acid pitc esderived from sulfuric; acid refining Lot petroleum oils.

A out 4 bv'v vme of..t:he-.:totalc ndensate:

boils at temperatureoi about. 5 225 10., and the remainder at about; 2255400916,; ."I jc preferred product of the; invention is; anzoil having a boiling point ran cf zar-4.00s Iii-des ed su a pr ductmav-be fractionat d out o t vapors-leaving ,thejdisti-llhtion. zone. or; the; total exit of thedistillation e-maybe liquefied and the condensate redistilledto recover the preferred 2.2574110. C. out which; is cheapest-p t t. dark brown. on: .havinaa. c eans t rpene-like odor,:-an.d which-ha's-heen ound to may; vary. cpnsiderli htly be particularly valuable for use in compounding rubber and in manufacture of resins. Representative samples of this heavy fraction had specific gravity in the range of .0.990-0.996 at 25C., contained about 14% parafiin' type hydrocarbons by the sulfonation test method, and had viscosity of '75 centipoises at 25 C.

We find that by carrying out destructive distillation of acid pitches of the type specified under the particular described conditions of atmospheric pressure, temperature and time, the mass in the distillation zone remains throughout the heating period in a distillable condition, the sought-for oils are not decomposed, and condensate in the condenser does not become viscous but retains a readily fiowable condition, and high yields of the order of 30-42% by weight of the acid pitch [charged into the still may be obtained.

In the practice of one example of the invention, the-acid sludge usedwas that resulting from a commercial operation in which.66 B. sulfuric acid was used for purificationof crudebenzoltoluol from drip oil, and the approximate composition of acid sludge was by weight 29% E2804, 9% oil and naphthalene, and 47% pitch. A

quantity of this acid sludge was diluted with about 20% by weight of water, agitated, and

boiledior about 15minutes. After settling for about 3 hours, the :under'layer'oi weaksulfuric acid, having an H2304" concentration of; about was drawn off.

1000 parts byweight of the acid pitch were.

mixed with 2130 parts by weight ofan aqueous. solution having an NaOI-I concentration of about 11%. The mass was agitated at temperature-of about 25 C. for about 1 hour. J The. mass was settled and the: supernatant aqueous. phase, .was

The neutralizedxacidpitch was; charged into a cold still. adapted to be. externally heated. Heating was controlled so that temperaturein the still was raised by' a relatively smooth gradient, to a point such that maximum vapor temperatureof vapors exiting the still was'about 395 vC. Distillation'was' carried outat atmospheric pressure,'and.untilthe" residue in the still, was reduced to a relatively dry, solidcoke-like mass. Distillation time was 3. hours. The vapors exitingthe distillation. zone were. condensed. in

a simple. total condenser, and-during the: entire operation, the distillate in. the condenser re? mained completely fluid...Th'er.e were recovered 315 parts by weight of oil'ha-vin'g a boilingpoint rangeof 78-394? C., yieldamounting to 31.5%

onthe basis of the acid pitch mass char ed'dntothe still.

Use .of the herein described .oils; in the. 1118,1111! iactureof resins. is claimed in Allen. and'Kerr- U. S. application Serial NO. 619,425, filed. September 29,.-1945, and use of such oils. in:.the compounding of rubber is. claimed :in Cole U. S. ape plioation Serial No'. .659,4'30,filed April .3, 19.46..

We claim:

1. The method for making-an oil-which comprises treating acid sludge, resulting. from the sul' furic acid purification of coal tar'distil'late, with waterunder conditions-to form a.- mass. comprise ing acid pitch and aqueous relatively zweakxsula furio acid, separating the .aci'dz'pitch from-at; least most of the. weak sulfuric. acid, treating: the :acid.

pitch with: neutralizing agent under. cOIiditiOlisitQ substantiallycompletelv neutralize remainingsulfuric acid associated" witlnthe acid pitch; separate ing from the; acidpitch.substantiallyrall zof, any.

residual aqueous phase resulting from said neutralization operation, subjecting the neutralized acid pitch to destructive distillation at atmospheric pressure by gradual external heating and at temperature such that vapor temperature of the oil vapors exiting the distillation zone does not substantially exceed 400 C. and for a period of time such that the distillation zone residue is reduced to a relatively solid coke-like mass, condensing the oil vapors exiting the distillation zone and recoverin an oil fraction boiling within the range of substantially 75-400 C.

2. The method for making an oil which comprises treating acid sludge, resulting from the sul furic acid purification of coal tar distillate, with Water under conditions to form a mass comprising acid pitch and aqueous relatively weak sulfuric acid, separating the acid pitch from at least most of the weak sulfuric acid, treating the acid pit-ch with neutralizing agent under conditions to substantially completely neutralize remaining sulfuric [acid associated with the acid pitch, separating from the acid pitch substantially all of any residual aqueous phase resulting from said neutralization operation, subjecting the neutralized acid pitch to destructive distillation at atmospheric pressure by gradual external heating and at temperature such that vapor temperature of the oil vapors exiting the distillation zone does not substantially exceed 400 C. and for a period of time such that the distillation zone residue is reduced to a relatively solid coke-like mass, condensing the oil vapors exitingthe distillation zone, and recovering an oil fraction having a boiling point range of ubstantially 225-400" C.

3. The method for making an oil which comprises treating acid sludge, resulting from the sulfuric acid purification of coal tar distillate, with water at elevated temperature under conditions to form a mass comprising acid pitch and aqueous relatively weak sulfuric acid, separating the acid pitch from at least most of the weak sulfuric acid, treating the acid pitch with an aqueous solution of neutralizing agent at about the boiling temperature of resulting mass for a period of time sufficient to substantially completely neutralize remaining sulfuric acid associated with the acid pit-ch, separating from the acid pitch substantial- 1y all of the residual aqueous phase resulting from said neutralization operation, subjecting the neutralized acid pitch to destructive distillation at atmospheric pressure by gradual external heating and at temperature such that vapor temperature of the oil vapors exiting the distillation zone does not substantially exceed 400 C. and for a period of time such that the distillation zone residue is reduced to a relatively solid coke-like mass, condensing the oil vapors exiting the distillation zone and recovering an oil fraction boiling within the range of substantially 75-400 C.

4. The method for making an oil which comprises treating acid sludge, resulting from the sul furic acid purification of coal tar distillate, with water at elevated temperature under conditions to form a mass comprising acid pitch and aqueous relatively weak sulfuric acid, separating the acid pitch from at least most of the weak sulfuric acid, treating the acid pitch with an aqueous solution of neutralizing agent at about the boiling temperature of the resulting mass for a period of time suflicient to substantially completely neutralize remaining sulfuric acid associated with the acid pitch, separating from the acid pitch substantially all of the residual aqueou phase resulting from said neutralization operation, subjecting the neutralized acid pitch to destructive distillation at atmospheric pressure by gradual external heating and at temperature such that vapor temper-- ature of the oil vapors exiting the distillation zone does not substantially exceed 400 C. and for a period of time such that the distillation zone residue is reduced to a relatively solid coke-like mass, condensing the oil vapors exiting the distillation zone, and recovering an oil fraction having a boiling point range of substantially 225-400 C.

5. The method for making an oil which comprises subjecting to destructive distillation, substantially completely neutralized acid pitch derived frcm acid sludge resulting from the sulfuric acid purification of coal tar distillate, said distillation operation being carried out at atmospheric pressure and by gradual external heating at temperature such that vapor temperature of the oil vapors exiting the distillation zone does not substantially exceed 400 C. and for a period of time such that the distillation zone residue is reduced to a relatively solid coke-like mass, condensing the oil vapors exiting the distillation zone and recovering an oil fraction boiling within the range of substantially TS-400 C.

HARRY L. ALLEN. GEORGE J. SKRIVER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS FOREIGN PATENTS Country Date Great Britain Feb. 8, 1937 Germany Feb, 26, 1938 Number Number 

